First wash and soak 2 cups idli rice, ¾ cup rice flakes and 2 tablespoon sago in enough water for at least 6 hours.
Similarly, soak ¾ cup whole urad dal in enough water for at least 6 hours.
Grind the urad dal mixture in to a fluffy, soft and smooth batter in a blender. Pulse a few times and grind in small intervals so that the batter is not heated up. Do not pour water but sprinkle some as needed to get the smooth texture. Remove it into a mixing bowl/container.
Add soaked rice mixture in batches into the blender.
Adding enough water as needed, grind into a coarse paste. It should feel grainy to touch. Remove it into the same container with urad dal batter.
Add salt as needed (I added about a tsp).
Using clean hand, mix it well together until both the batters are incorporated together.
Leave it to ferment in a warm place for 8-10 hours. If it is cold outside, try placing the container in a pre-heated oven and leave it overnight for best results.
The batter should double in volume and look fluffy.
Gently beat it down so that the batter is well mixed using a ladle.
Set the idli steamer with enough water on medium heat. Meanwhile brush the idli plates with a drop of oil all over.
Fill each idli plate with batter until it is half full.
Place the filled idli plates carefully into the idli stand. Lock the plates in position.
Set the idli stand in the steamer and close the lid. If you are using pressure cooker, do not put the cooker weight on.
Steam for 10-11 mins on medium high flame. Check if the idlis are done by touching the top, if it is not sticky, remove from heat.
Let the plates cool down on the counter for 5-7 mins.
Run a knife through the edges and gently unmould the idlis.
The idlis should come off without sticking at the bottom of the plate.
Serve hot/warm with Hotel style coconut chutney and tiffin sambar.
Leftover batter can be stored in an airtight container in fridge for 3-4 days.
The same batter can be made in regular idli mould too.